Implantable apparatuses which are provided with electronic devices, such as circuit boards or the like, are frequently used in the field of medicine. Electronic devices such as cardiac pacemakers and defibrillators, or neurological devices, such as cerebral pacemakers for deep brain stimulation, spinal cord stimulation devices, TENS (transcutaneous electrical nerve stimulators), or devices for muscular stimulation therapy, as well as diagnostic apparatuses, which assay the chemical properties of the blood of the patient or other body parts or other body characteristics, use electrodes which are guided through the body of the patient and are electrically connected to the implantable apparatus. The implantable electronic apparatus often has an essentially socket-shaped or hollow-cylindrical connection apparatus (socket, contact pin) for this purpose, in the form of a contact assembly, into which the plug of the electrode line is inserted to produce an electrical connection between the electrode and the electronic apparatus situated in the implantable apparatus. The connection apparatus is often referred to as a header. An essentially cylindrical plug having a contact assembly, which is inserted into the socket to produce the electrical connection, is also provided on the electrode line which has the electrode.
In the future, multi-pole plugs having more than two poles will be increasingly used. For example, the plug according to the standard IS-4 is a 4-pole plug which has an essentially cylindrical shape and has four electrically conductive contact sections which are situated neighboring one another in the axial direction.
An essentially cylindrical plug, which may be inserted into a socket, is specified in U.S. Pat. No. 4,469,104. For this purpose, the socket has an essentially cylindrical opening. Three contact configurations situated one behind another in the direction of the longitudinal axis are provided on the multi-pole plug, which are each separated from one another by insulating areas. A conductive ring in the form of a woven metal toroid is situated in a retention element provided with a groove. The toroid is produced from a leaf-shaped woven metal. After the toroid has been shaped by rolling up the leaf-shaped material, the material is welded together on its ends to form a closed elastic ring. The conductive ring is situated in the retention element in such a way that it projects slightly beyond the lateral surface of the adjoining areas of the plug. After the plug is inserted into the opening of the contact assembly, the conductive ring contacts the contact sections situated on the socket, each of which has the form of a metal ring. An electrical connection is thus produced between the particular contact configuration on the plug and the contact section of the socket to electrically connect the electrode to the electronic apparatus in the implantable device.
In the publication WO 2005/014108, a contact configuration for connecting an electrode and an implantable medical device is described. The contact configuration has a connection clip which comprises a single wire and is shaped in such a way that it has a first spring arm and a second spring arm. Both spring arms adjoin an upper curved section which forms the upper section of the connection clip. The spring arms have essentially linear lateral sections, which extend from the upper curved section to a lower curved section. The connection clip is situated in a partially bent-up position in the housing of the contact configuration having a through opening. The connection clip is situated in the housing of the contact configuration in such a way that it projects slightly inward in the radial direction from the housing. The housing is shaped for this purpose in such a way that after the plug is inserted into the opening of the contact configuration, the connection clip is pressed further outward in the radial direction, so that a connection between plug and electronic device is produced.
An implantable electronic device having a regulating device for the plug and an electrode line connectable to the device is known from the document EP 1 062 986 B1. The electronic device has an essentially socket-shaped connection apparatus for the plug of the electrode line to the regulating device, which is formed by a manually operable, eccentrically mounted clamping cam and a contact element provided in the connection apparatus for the different pole of the plug of a coaxial electrode line to be connected to the cardiac pacemaker. The eccentrically mounted clamping cam is operationally linked at its edge to the contact element, so that a rotational movement of the clamping cam is transmitted to the contact element. The contact element, which encloses the different pole of the plug in a formfitting way, is thus reversibly deformed in such a way that a friction-locked connection results between the different pole and the contact element, which fixes the plug inside the connection apparatus and simultaneously ensures a good electrical contact between the contact element and the different pole of the plug.
An electrical connector, in particular a medically implantable electrical connector having a housing and a through hole is known from the publication WO 2005/105207 A2. A spring is situated in a groove of the housing, which is used for the purpose of scraping off a coating (typically an oxide layer) from the surface of the groove and the plug surface, so that a reduced resistance and a reduced resistance variability are achieved. In particular, the spring is implemented as a diagonally lying coiled spring.
An electrical contact having a spring ring is also known from the publication US 2006/0047322 A1. This publication discloses a contact assembly having multiple contact configurations having electrically conductive spring rings, which are provided in corresponding depressions of the contact configurations.
A contact assembly which has multiple contact configurations having annular spring contacts is described in U.S. Pat. No. 4,995,389.
A contact configuration for connecting an electrode line to an implantable device is known from the publication DE 10 2004 017 659 A1. The contact configuration has an electrical terminal socket having a socket longitudinal axis and at least one opening for inserting a plug along the socket longitudinal axis. A one-piece metallic spring contact tongue having spring contact tongue sections running transversely to the spring deflection direction, which are connected to one another by coil sections, is provided as the contact element. The spring contact tongue is particularly used in such a way that it has a wavy shape, such as an S-shaped wavy shape.
A contact element made of a one-piece metallic spring contact tongue is also specified in the publication US 2005/0261745 A1. Multiple contact elements are bent here in such a way that their end section extends into the opening and forms a tangent on an imaginary circle, which has a smaller diameter than the opening of the electrode configuration for the plug. In this publication, a second variation of a contact configuration is also described, in which the contact elements comprise rod-shaped elements, whose end sections are directed away from the opening for the plug. Analogously to the leaf-shaped elements, the rod-shaped elements are bent in such a way that they form a tangent on an imaginary circle which has a smaller diameter than the cross-section of the plug opening.
A further possibility for a contact configuration is disclosed in the publication US 2002/0128692 A1. The contact configuration contains annular spring elements in which circular openings are provided. Spherical contact elements are situated in the circular openings, which are pressed by the spring action of the spring in the direction away from the opening, but project somewhat therein, so that a contact is produced between the inserted plug and the metal balls.
High-precision and therefore costly manufacturing devices are necessary for producing the above-mentioned contact configurations having metallic spring elements or tongues. These contact elements are typically from a strip material produced via a punching-bending process in a progressive composite die. For example, a rectangular sheet metal strip is generated, which is reshaped over the longer side in such a way that it becomes the lateral surface of a tube which is not entirely closed. By punching out segments in the direction of the shorter side from this lateral surface, a specific number of webs arise. These webs are reshaped to half the height of the lateral surface in such a way that they project radially inward uniformly and thus form a constriction in the lateral surface, via which the electrical contact may occur later. A contact element of this type does not have a defined radius, however, via which a contact force on a cylindrical plug may be adjusted. A functional contact assembly first arises when a contact element is inserted into the hole of a dimensionally stable sleeve with radial pretension.
The contact materials which are common in everyday electronic apparatuses and are therefore also cost-effective may not be used in long-term implants, because in addition to the rather general criterion of corrosion stability, the criterion of biocompatibility must also be fulfilled. For materials which are not frequently used, however, the continuous availability of the materials needed for running production may be problematic.
For a stable electrical contact of a plug-in connection, a macroscopic minimum contact pressure between the contact partners of plug and socket is primarily needed. This minimum contact pressure for a single contact is a function of the materials used, in a first approximation, a normal force of greater than 1 N may be used. If a minimum contact pressure of this type is not achieved, electrically insulating cover layers of the material surfaces may not be removed in the contact area and, in addition, the long-term stability of the electrical contact is not ensured.
In the constructive mechanical design of a plug contact system, however, the plugability must also be ensured. A parameter for this purpose is the maximum permissible insertion force. The spring rigidity of the contact elements may not be increased arbitrarily to thus achieve better electrical contact security, because otherwise problems may occur in the plugging procedure.
Therefore, for a stable electrical contact it is necessary for the mechanical tension built up upon insertion of the cylindrical plug (contact end) to be so great that electrically insulating cover layers which interfere in the contact area are removed, so that the contact partners may come into direct metallic contact. For chronological consistency of the electrical contact resistance, the contact area thus produced must remain metallically conductive over the entire duration of the contact. It is accordingly to be ensured by the construction that such a contact may not lift off (breathe) in the event of weak mechanical tension and under radial mechanical load. However, it is also to be ensured that a contact of this type does not begin to rub in the event of strong mechanical pretension and axial mechanical load, because friction corrosion (fretting) may thus occur.